This invention relates to a method and apparatus for sealing packages or bundles of product cartons on a conveyor line. In particular, the invention pertains to improved sealing apparatus for individually sealing with film a series or succession of product packages rapidly and efficiently.
Many products are shipped and displayed for sale to the public in cartons. Currently, many products are sold in large volumes to small businesses or consumers in warehouse stores and the like. Large volume sales require manufacturers to bundle or attach cartons together using shrinkwrap film and the like. In the sale of facial tissue cartons, for example, it is common to bundle together six, eight, ten or more cartons in a shrinkwrap film package for sale to consumers.
Apparatus for shrinkwrapping cartons together must be capable of rapidly, efficiently, and automatically stacking cartons together in a bundle, wrapping them with film, and sealing the bundle. The process must occur rapidly, and usually is most efficiently performed in a series of steps along a conveyor line. Sealing the shrinkwrap film tightly and securely around the bundle of cartons is necessary to provide a tight bundle that will maintain its integrity during shipment of the products.
One challenge in shrinkwrapping cartons is to improve the speed of the operation so that more cartons per unit time may be wrapped. Heat sealing of shrinkwrapped film requires physically holding together for a predetermined time period two opposing film surfaces. When sealing a convoy or series of bundles in succession, it is usually necessary to move the cartons along a predetermined path in bundles, and then seal each carton on both ends using a sealing mechanism. Many times the sealing mechanism is capable of holding together in close proximity two film surfaces at the end of a bundle. A method and apparatus that can accurately and quickly perform these steps is highly desirable.
An apparatus and method is provided for sealing bundles of cartons that are passed in series along a moving conveyor line. A frame is aligned with the conveyor, and a movable carriage assembly is connected to the frame. Packages or cartons of product are stacked and bundled by film, such as thermoplastic film, in a series of sealing steps. The apparatus includes at least one motor mounted on the frame which is capable of engaging the carriage assembly to facilitate reciprocating (i.e. back and forth) movement of the carriage assembly in relation to the moving packages. A separate computer controlled servo motor may be employed in some embodiments of the invention to drive the opening and closing of seal bars on the carriage assembly to effect sealing of the film at each end of the package. This drive may use a belt to apply force to the seal bars.
In one embodiment of the invention, a second motor, such as a servo motor, is mounted on the stationary frame. The motor is adapted to engage the carriage assembly to move the upper and lower seal bars in relation to one another, opening and closing the seal nip. In another embodiment of the invention, the first motor means comprises at least one servo drive. In some embodiments, a pair of servo linear slide modules move the carriage back and forth along the conveyor line. The apparatus may contain a second motor that is controlled by electronic signals generated using a microprocessor.
A method of sealing packages with film using a sealing mechanism connected to a reciprocating carriage is disclosed, comprising several steps. First, a first package is provided and surrounded by a film. Then, the step of closing the sealing mechanism upon the film is accomplished, thereby sealing the film on a first end of the first package. A next step involves opening the sealing mechanism. Next, at a predetermined time the carriage is moved in relation to the first package. A next step relates to closing the sealing mechanism upon the film, thereby sealing the film on a second end of the first package. Multiple packages may be sealed in series by repeating the steps of the method. In some applications, the second end of each package is adjacent the first end of the next package in series. The closing of the sealing mechanism upon the film may seal the film on a second end of the first package while simultaneously sealing the first end of a second package. This is so because the packages (bundles of product cartons) may be oriented end-to-end on a conveyor line.